(1) Field of the Invention
The present invention relates to a refrigerator, and more particularly, to a refrigerating cycle system for a refrigerator, which can realize quick cooling during an initial operation of the refrigerator and maintain high efficiency during a normal operation of the refrigerator.
(2) Description of Related Art
Generally, a refrigerating cycle system used in a refrigerator or an air conditioner absorbs heat while a refrigerant is changed from a liquid phase into a vapor phase, and discharges the heat while the vapor phase is changed into the liquid phase. That is, the cooling operation is realized by heat exchange occurring when the phase of the refrigerant is changed.
U.S. Pat. No. 5,406,805 discloses a conventional refrigerating cycle system for a refrigerator. The refrigerating cycle system of this patent, as shown in the attached FIG. 1, comprises a compressor 20, a condenser 21, an expansion device 22, a first evaporator 23 for a freezing chamber, and a second evaporator 24 for a refrigerating chamber. These elements are connected in order by a cooling tube 25 to constitute a closed cycle. The first and second evaporators 23 and 24 and the condenser 21 are respectively provided with first, second and third air fans 23a, 24a and 21a so as to circulate air. The first and second evaporators 23 and 24 are interconnected in series so that the entirety of the refrigerant passing through the first evaporator 23 can flow into the second evaporator 24. The phase of the refrigerant is changed while flowing along the cooling tube 25 in a direction as indicated by arrows.
Describing more in detail, the refrigerant is evaporated while passing through the first and second evaporators 23 and 24 to absorb heat from the surrounding air, thereby generating cool air. The cool air is forced to the freezing and refrigerating chambers by the first and second air fans 23a and 24a.
FIG. 2 shows a detailed view of the second evaporator 24 for the refrigerating chamber. The second evaporator 24 is an intercooler evaporator comprising an inner tube 26a and an outer tube 26b enclosing the inner tube 26a. The refrigerant fed from the condenser 21 is supplied to the expansion device 22 through the inner tube 26a while the refrigerant fed from the first evaporator 23 is fed to the compressor 20 through the outer tube 26b. At this point, the refrigerant passing through the outer tube 26b is a two-phase refrigerant, which is a mixture of a liquid-phase refrigerant and a vapor-phase refrigerant. The two-phase refrigerant is used for a cooling process of the refrigerating chamber after flowing into the second evaporator 24 through the outer tube 26b. After this, the two-phase refrigerant is changed into the vapor-phase refrigerant and is then fed to the compressor 20. By using the above described intercooler evaporator, the refrigerant, which flows along the outer tube 26b of the second evaporator 24 after passing through the first evaporator 23, is used for cooling the refrigerating chamber as well as for sub-cooling the liquid refrigerant flowing along the inner tube 26a by a heat exchange. That is, since the liquid refrigerant fed to the expansion device 22 is subcooled by the heat exchange with the refrigerant flowing along the outer tube 26b, the efficiency of the refrigerating cycle system is increased.
However, the heat exchange between the high temperature liquid refrigerant from the condenser and the low temperature refrigerant passing through the first evaporator 23 occurs at the second evaporator 24, resulting in heat-load. As a result, the cooling performance of the refrigerating chamber is reduced. That is, when initially operating the refrigerator or reusing the same after being inactive for a long time, considerable time for lowering the temperature of the refrigerating chamber to a predetermined level is required. In addition, when there occurs a frequent opening of the refrigerator door which increases the temperature of the refrigerating chamber, it is impossible to rapidly reduce the temperature of the refrigerating chamber.